Question on "Continuously Scrolling Image" tutorial

Okay I was all, yay, a super-easy tutorial, looks nice.
( “Continuously scrolling image” …
http://www.kirupa.com/developer/flash5/imagescroll.htm )

But when I make it with my own images, when I preview, the first entire half of the scrolling alpha image comes across as a bunch of horizontal lines. If change the starting point of the image to past halfway (beyond the middle dot of the graphic), it plays fine.

This is driving me ABSOLUTELY INSANE. I’ve tried other images, they all do the same thing. Straight horizontal lines, then past midway point, the right image starts and continues correctly.

PLEASE if anyone knows what I’m talking about, please reply, I’ve been pulling my hair out over this, it doesn’t make any sense at all. >_<